The disclosure relates to a control device and a method for controlling an induction machine, in particular a rotating or linear induction machine of an electrical drive system of an electrically operated vehicle.
When controlling an induction machine, by way of example in an electrical drive system of an electrically operated vehicle, it is crucial to know the position of the rotor relative to the stator of the induction machine. In order to provide a required torque using an induction machine, a rotating electrical field that rotates in a synchronized manner with the rotor is generated in the stator of the machine. The prevailing angle of the rotor is required for the control process for the purpose of generating this field.
One possibility for the purpose of determining the rotor position is to use mechanical, optical or magnetic sensors. However, these are expensive and require corresponding installation space in the electrical drive system. An alternative possibility for the purpose of determining the rotor angle is to measure voltages in the phase lines of the induction machine during different phase current configuration in the induction machine in order to draw conclusions regarding the prevailing rotor angle on the basis of the system response of the induction machine. It is not necessary to use external sensors for this purpose.
By way of example, the publication DE 10 2009 029 896 A1 discloses a method for determining the armature position of an induction machine and said method evaluates the electrical response of the induction machine to two voltage pulses that are time offset with respect to one another and are located perpendicular to one another.
The publication WO 92/01331 A1 discloses a switching arrangement for detecting the angle of rotation of an electrical machine without the use of sensors, in which arrangement of the voltage pulses that are generated by means of an inverter that is supplying the electrical machine are used as electrical measuring signals for the purpose of detecting the angle of rotation.
The publication DE 102 26 974 A1 discloses a method for determining the angle position of a rotor of an electrical machine without the use of sensors and said method uses for the purpose of pulse width modulation synchronous field-oriented test space diagrams for the purpose of generating a ripple content that is dependent upon test signals and said ripple content can in turn be evaluated for the purpose of determining the position angle.
In the case of conventional methods, it is necessary in each case to temporarily interrupt the operation of the modulation unit that generates the modulated control signals for the actual operation of the induction machine in order to be able to supply voltage pulses to the phase lines for the purpose of measuring the system response of the induction machine. As a consequence, undesired voltage and/or current fluctuations or ripples can occur at the input connectors of the induction machine.
There is therefore a demand for solutions for determining the rotor angle without the use of sensors, in which the voltage and/or current fluctuations can be minimized and the current and voltage sensor technology can be simplified.